One process for separation of liquid hydrocarbons containing two or more carbon atoms (ethane product) from LNG and to produce natural gas meeting pipeline specifications is disclosed in U.S. Pat. No. 6,564,579. That process comprises: vaporizing the LNG to produce a partially vaporized natural gas stream; fractionating the partially vaporized natural gas stream to produce a gas stream and a liquid stream(ethane product); compressing the gas stream to increase the pressure of the gas stream by about 50 to about 150 psi to produce a compressed gas stream and cooling the compressed gas stream by heat exchange with the stream of LNG to produce a liquid compressed stream; pumping the liquid compressed stream to produce a high-pressure liquid stream at a pressure from about 800 to about 1200 psig; vaporizing the high pressure liquid stream to produce a conditioned natural gas suitable for delivery to a pipeline or for commercial use; recovering the liquid ethane product.
In that process, the distillation column comprises only one stripping section and uses as a reflux the liquid of the partially vaporized natural gas stream. This severely limits the possibilities of enriching methane content in the distillation column overhead stream, and requires a great fraction of liquid in the partially vaporized natural gas stream. In addition, compressing of the enriched in methane gas stream is carried out at low temperatures. In so doing, much heat is introduced in the system, not only from the distillation column reboiler but also from the compressor. This does not allow production of the enriched in methane stream in fully liquid state for the end user, without also using outside refrigeration. There is need for an improved process for separation of LNG to produce a methane enriched product, and an ethane enriched product.